The present invention relates generally to improvements in fastener driving tools, and specifically to such tools used in the installation of trim, other decorative applications and finishing applications utilizing relatively small fasteners, fasteners made of relatively thin wire stock, and/or used with relatively small and/or delicate workpieces. The foregoing will generally be referred to as xe2x80x9ctrim applications.xe2x80x9d Included in the present tool are several features intended to make the manufacture, use and/or repair of such tools more efficient.
Portable combustion powered tools for use in driving fasteners into workpieces are described in commonly assigned patents to Nikolich, U.S. Pat. Nos. Re. 32,452; 4,403,722; 4,483,473; 4,483,474; 4,552,162; 5,197,646 and 5,263,439, all of which are incorporated herein by reference. Such combustion powered tools particularly designed for trim applications are disclosed in commonly assigned U.S. Pat. No. 6,016,622, also incorporated by reference herein. Similar combustion powered nail and staple driving tools are available from ITW-Paslode under the IMPULSE(copyright) brand.
Such tools incorporate a generally pistol-shaped tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas also called a fuel cell. A battery-powered electronic power distribution unit or electronic sending unit produces the spark for ignition, and a fan located in the combustion chamber provides for both an efficient combustion within the chamber, and facilitates scavenging, including the exhaust of combustion by-products. The engine includes a reciprocating piston having an elongate, rigid driver blade disposed within a piston chamber of a cylinder body.
A wall of the combustion chamber is axially reciprocable about a valve sleeve and, through a linkage, moves to close the combustion chamber when a workpiece contact element at the end of a nosepiece, or nosepiece assembly, connected to the linkage is pressed against a workpiece. This pressing action also triggers the introduction of a specified volume of fuel gas into the combustion chamber from the fuel cell.
Upon the pulling of a trigger, which causes the ignition of the gas in the combustion chamber, the piston and the driver blade are shot downward to impact a positioned fastener and drive it into the workpiece. As the piston is driven downward, a displacement volume enclosed in the piston chamber below the piston is forced to exit through one or more exit ports provided at a lower end of the cylinder. After impact, the piston then returns to its original or xe2x80x9creadyxe2x80x9d position through differential gas pressures within the cylinder. Fasteners are fed into the nosepiece from a supply assembly, such as a magazine, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
One operational characteristic of such tools employed in trim applications is that commercially available fasteners are typically provided in elgongate strips of individual fasteners held together with adhesive, not unlike conventional office staples. It is common for such fasteners to become jammed in the nosepiece. Thus, provisions are made in known trim-type fastener driving tools for the user to access the interior of the nosepiece to remove the jammed fasteners.
In one known embodiment, a front plate of the nosepiece assembly is pivotable outward to permit full access to the interior of the nosepiece. The front plate is preferably pivotable to at least 90xc2x0 relative to the vertical operational axis of the tool for enabling the operator to pull out the jammed fasteners perpendicularly to the action of the piston. One drawback of such an arrangement is that if the operator neglects to relieve the spring pressure of the magazine against the fasteners, once the jam is cleared, additional fasteners may be uncontrollably ejected from the nosepiece, potentially causing injury or damage.
Another operational characteristic of known trim-type fastener driving tools is that, to avoid user fatigue, designers are constantly trying to improve the ergonomics of the tool, including reducing weight and adjusting balance. One aspect of such a design objective is that the nosepiece has been moved closer to the combustion chamber to reduce the height of the tool. A drawback of this type of design is that the pivoting action of the front plate is restricted, and can no longer reach a fully open position. This restricts access to the jammed fasteners, in that the user must work around the partially-opened front plate to access the jam. However, an advantage of this restricted pivoting action is that if the magazine spring force has not been disconnected, upon clearing of a jam, fasteners ejected from the nosepiece are deflected by the front plate to avoid injury and/or damage.
Another operational characteristic of such tools is that significant impact forces are generated in the combustion and driving of the driver blade. Also, the tools are sometimes dropped from a height during use or transport. These impacts have been known to damage the sensitive electronic components of the tool, such as, but not limited to the electronic sending unit. To reduce such impacts, it is known to apply a shock absorbing caulk around the sending unit, which in some tools is located inside the handle portion. However, a drawback of this technique is that the caulk is messy to apply during manufacturing, and also makes service and repair of the sending unit more difficult.
Still another operational characteristic of such tools is that it is important to avoid firing the tool when the magazine is empty of fasteners. If so, the driver blade can cause a mark in the workpiece, which is very undesirable in appearance-intensive trim applications. It is known to provide magazines with indicators of the impending depletion of the fasteners in the magazine. However, these known devices do not provide the number of fasteners remaining just prior to the emptying of the magazine. Since operators of such tools often change the type and/or length of fasteners, it is desirable to have an accurate indication of when the magazine will become depleted.
Thus, it is an object of the present invention to provide an improved fastener driving tool which provides for the deflection of ejected fasteners upon the clearance of a fastener jam, and also is fully openable for the clearance of more complicated jams, or jams of longer fasteners.
Another object of the present invention is to provide an improved fastener driving tool which has a relatively short profile, but is also fully accessible for clearing jammed fasteners.
Still another object of the present invention is to provide an improved fastener driving tool in which the handle portion provides shock absorption to the electronic sending unit without the use of shock absorbing caulk.
A further object of the present invention is to provide an improved fastener driving tool having a fastener magazine with an indicator of the number of fasteners remaining just before the magazine is depleted.
The above-listed objects are met or exceeded by the present trim-type fastener driving tool, which features a front plate which is pivotable relative to the nosepiece to permit access, and which has two jam clearing positions: a first position which deflects fasteners ejected after the jam is cleared, and a second, fully accessible open position which permits axial extraction of jammed fasteners. In addition, the handle portion is preferably provided in its interior with a resilient cushion for protecting a delicate item stored within the handle, such as an electronic sending unit, which avoids the use of shock-absorbing caulk. Preferably, the cushion is part of a resilient gripping surface found on the outside of the handle. Also, the magazine is preferably provided with an indicator of the number of fasteners remaining just before the magazine becomes depleted.
More specifically, a powered tool constructed to axially drive a driver blade to impact and drive a fastener into a workpiece includes a nosepiece assembly including a back plate and a front plate combining to define a path for the driver blade, the front plate being pivotally movable relative to the back plate between a closed position, in which the front plate and the back plate are in contact with each other, and an open position. The front plate is movable to an interim deflecting position between the closed position and the open position.
In an alternate embodiment, a powered tool constructed to axially drive a driver blade to impact and drive a fastener into a workpiece includes a handle portion with an outer surface at least partially defining a grip, and an inner surface at least partially defining a chamber, preferably for an electronic sending unit. The handle portion includes a substrate having at least one aperture, and an overmold configured for forming a gripping surface on the outer surface, the overmold also being configured for extending through at least one of the apertures into the chamber for forming at least one resilient mounting point for the electronic sending unit.
In a further alternate embodiment, a powered tool constructed to axially drive a driver blade to impact and drive a fastener into a workpiece includes a nosepiece assembly including a back plate defining an aperture through which fasteners are fed for engagement with the driver blade, a front plate at least partially covering the aperture, and a magazine for dispensing fasteners to the aperture. The magazine has an indicator for indicating how many fasteners are remaining just prior to the magazine becoming empty.